C-type natriuretic peptide (CNP) is a vasoactive peptide that has vasodilatory and diuretic properties. CNP is a potent relaxant of vascular smooth muscle, particularly in the coronary circulation. CNP also inhibits smooth muscle cell proliferation and aldosterone production. CNP is also an atherogenic agent, i.e. has antiaggregatory and anticoagulant properties, and is an anti-inflammatory. The biological actions of CNP are mediated via activation of specific natriuretic peptide receptors (NPR5), particularly the NPR-B and -C subtypes. NPR-C is the predominant subtype involved in the vasorelaxant response to CNP (Chauhan, S. D. et al, (2003) Proceedings of the National Academy of Sciences, 100, 3, 1426-1431).
CNP has been found to be useful in the prevention and treatment of ischemic vascular disease, e.g. myocardial infarction or stroke, and other cardiovascular disorders, e.g. hypertension, atherosclerosis, restenosis, and myocardial ischaemia/reperfusion injury (Hobbs, A., et al, (2004), Circulation, 110, 1231-1235). CNP has also been found to exert a strong anti-atherogenic influence on blood vessel walls (Ahluwali, A., et al, (2005) Trends in Pharmacological Sciences, 26, 3, 162-167).
CNP is therefore potentially useful in treating a wide range of vascular disorders. There are, of course, disadvantages associated with using a protein-based drug in a therapeutic context. In particular, oral administration results in the rapid hydrolysis of amide bonds in the protein, leading to the destruction of the protein and loss of therapeutic efficacy in vivo. There is therefore a need to provide small molecules that mimic CNP and which do not degrade easily when administered in a therapeutic context.